Previous research has defined "aggregate pesticide expenditures" as the control variable; however, virtually all managerial recommendations and environmental restrictions target specific pesticides, rates, and crops. A bioeconomic approach considering particular pesticides on specific pests and crops is recommended for managerial-policy applications and testing for increasing returns. Exponential weed control and seven popular yield damage functional forms were estimated for a bioeconomic weed control model for winter wheat in Washington. Concavity with respect to herbicide rate was observed for most popular damage functions at normal weed densities and manufacturers' label rates, but convexity existed outside these ranges and should be checked.